On 05/04/2015 09:53 AM, Jason Space wrote:
> First off, my apologies if this is slightly OT, ...
It's not.
> ... but I'm looking for some
> help in the way(s) that Linux on z differs from Linux on open systems.
> I've been scouring the IBM redbooks and whitepapers to find tid-bits of
> information and presenting to the powers that be.
Rough enumeration of differences at the end of this reply.
But keep in mind (and keep reminding your powers that be) from a server
and business apps standpoint "Linux is Linux".
> Due to recent changes in our organization there has been a shift in the
> "who architects/engineers/administers" the Linux on z environment. The
> current momentum is to have the *NIX group essentially do all of it from
> the provisioning to administration. Bottom line is, they want to set it
> up like it is on the distributed systems (autoinstall vs, cloning, overuse
> of lvm, r/o binaries, etc..) some which I know fails to leverage the
> benefits of mainframe.
See below. But also perhaps "fails to leverage" full benefit of
virtualization on *any* platform. What I mean is, shared disk (just for
one example) is easily accomplished on other architectures. R/O binaries
is related. The tools used for stand-alone / discrete Linux instances
(eg: blades) often excludes really helpful methods. Not that you cannot
use tools such as Puppet (or Ansible, Salt, Vagrant ... you name it) in
a shared filesystems environment. Problem is the habits some sysadmins
fall into presume that all op sys is always writable. Not a good
assumption and not best practice.
I presume you are hosting zLinux on z/VM. That's your most cost
effective solution.
> 1. Some of the things the open systems *NIX guys like to do is LVM
> everything, including root. From the Set up Linux on IBM System z for
> Production redbook
> I found the following statement:
> "Do not include the root file system in the LVM structure
> because, if for any reason the LVM
> fails, the operating system will not boot. " - Set up
> Linux on IBM System z for Production
>
> Are there other reasoning's to not do so? These are the types of things
> that would really be helpful.
See other responses. However:
I run LVM heavily and have for 4 or 5 years now. I put the op sys into
its own LV, then /home and other non-OS content into other LVs.
Even apart from z, I boot from a different volume.
So for z, put your /boot onto its own small minidisk. Then let INITRD
magic bring up LVM smarts to get the VG(s) going.
> 2. No root access for z/VM system programmers to z/Linux servers.
> To my knowledge the s390-tools modules require root to invoke
> them. These tools are the essential interfaces between z/Linux and z/VM
> platform.
See other responses.
As the VM guy, you have other access to VM. But ... yeah ... your Linux
guys are hobbling you for no benefit. Do they similarly shut out the
VMware wranglers?
> 3. Sharing of Read/Only binaries.
> Install once / share many -- This idea of this is mainframe
> centric and is foreign idea to open systems.
What Mark and Mike said.
I run shared R/O "disk" on all platforms.
My home systems have a combination of Xen and KVM guests. The operating
system is on one R/O shared (virtual) disk. Each guest then has its own
R/W disk. Backing store is LVM when possible. (Non-LVM is mostly
historical: LVM is just too good to not use.)
I've talked about this so many times that the good readers of this list
must be tired of me.
> I guess these are the "big" ones, at least in my mind. At the end of the
> day, I realize that the best intentions and reasons often result in poor
> decisions by those that are in the position to make them.
Linux on z should really *not* be all that foreign to your Linux
staffers. For them, the mainframe should be just another hardware type:
I386, S390, ARM, PPC, SPARC, MIPS.
Linux on z differs from what they're used to ...
* no physical screen and keyboard (there is one, but that's the HMC)
* virtual console is text only (and is via 3270, which they will find
odd)
* disks can be CKD (3390) with tracks and records or FBA (9336, 3370,
VDISK) like they're used to
* more likely to use a virtual switch (go for Layer 2 if you can)
Neale Ferguson described VM/CP as a "smart BIOS".
Also, there was some discussion about consoles earlier this year.
http://www.mail-archive.com/linux-390%40vm.marist.edu/msg66855.html
> Thx,
> Jason
Skipping discussion of over-committing memory, partitionless disks, and
several TL/DR points. Maybe later.
-- R; <><
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